I dont know what is inside the precat. I can tell you that on my car, one of them was blocked solid, apparently melted and thus I had it replaced. I looked inside it, confirmed.

For my car, a 380sl, Miller, a leading aftermarket cat supplier, also sells the pipes with the precats. So you can buy everything from them. I think fastlane sells miller cats. If they dont try www.autopartsauthority.com. It is usually presented as one of the parts that can be ordered with the main cat.

Duke may be right about what is inside. I believe that my car (an MB CA car originally sold in maryland) passed pretty stiff emissions tests with one of the precats replaced with a straight pipe. Then again, there were question marks on a relatively new cat just a few years later. If it were me, if I had the money and the sound bothered me I would replace that pipe precat and not do a straightthrough without precat. If I did not jave the money, i would leave it alone. If you try to remove the pipe and reuse it after trying to get whatever is in there out, note the age and rust on the pipes may prevent them from being reused.